Hardest problem you'll have is with the crank pulley. The 7M ones have 3 serpentine belts and the 5M one won't fit a 6/7M crank. You'll need one off a 6M to work. I doubt you'd have to worry about the 7M pistons not working. They have such a huge dish that the valves could probably never hit. The downside is that you'll have a mega low compression ratio. Personally I'd buy a 6M or just use the entire 7MGTE engine (better choice).